This invention relates to a curvature measurement device, and more particularly to a device which can measure the continuous angular curvature or rotational curvature of an object. The invention has particular but not exclusive application to the measurement of the curvature of the human spine in connection with correct posture detectors.
In numerous fields of industry such as the construction industry or materials testing industry it is necessary to measure the curvature of a particular structural member, or to be able to continuously measure changes in curvature of such structural members. Most state of the art measurement devices for this purpose utilize strain gauges wherein a particular element such as a wire changes its dimension in accordance with changes in the curvature of the element to be measured. Some strain gauge devices utilize electrical resistance wires whose resistance changes as the dimensions of the wire change due to curvature of the object being measured. Other strain gauge devices utilize a wire in conjunction with a switch or other detecting element such that as the wire changes its dimensions in accordance with curvature of the element to be measured, the detecting device is triggered to produce an output signal.
While these devices may be satisfactory for some purposes, they generally are expensive and compplex because they require a special type of strain gauge element which is sufficiently sensitive to produce detectible results from even slight curvatures.
A specific application of such curvature measurement devices finds use in connection with poor posture detectors which are placed on the back of a wearer and detect spinal curvature. It is well known that malposition of the human spinal column is the cause of many ailments. Such ailments, as well as discomfort, can be avoided with correct posture; however, a patient is generally not aware of his poor posture position, By utilizing a curvature measurement device it is possible to provide the patient with greater spinal curvature awareness than he could achieve naturally.
One poor posture detector known in the art is described in U.S. Pat. No. 3,608,541. This device utilizes a flexible column hinged at one side thereof which has an actuating cable at the opposite side thereof which actuates a switch when the column is flexed greater than a given preset amount. While this device eliminates the necessity for a strain gauge detector, it cannot provide continuous signals proportional to any change in the curvature. In addition, because of its special construction, it is inherently limited in use to spinal curvature detection. Furthermore, the detector is limited to the use of one wire because of its peculiar construction. Still further, the detector described in the aforementioned patent can only detect angular curvature in a given plane but can not detect rotational curvature about a given axis.